Question

Give the mode of action of Bt cotton on bollworm.

Answer 1

Mode of action:

1. The bollworm larva feeds on Bt cotton and ingests Bt toxin in its inactive protoxin form.
2. The alkaline conditions in the larva’s gut solubilise the toxin crystals and activate the toxin.
3. The active toxin binds to cells lining the midgut and forms pores in them.
4. The gut cells swell and lyse, disrupting the larva’s gut. The larva stops feeding and eventually dies.

Bt cotton helps control bollworms and can reduce the need for insecticide spraying against these pests.